In the area of interactive displays, it may be desirable to achieve interaction—such as touch or gesture—in proximity to the display surface near the XY-position of the interaction. In some systems, it is known to position an array of cameras surrounding the perimeter around the display that may be used to sense gestures. However, there tend to be limits as to how close such interaction may be sensed—as well as difficulties achieving interaction in close proximity to the central region of the display by such means.
To compensate for these limits, some systems have employed a telecentric reverse-projection imaging system that may be used in conjunction with an LCD display, but such conventional imaging system may be bulky—thus, resulting in a display that may be thick. In order to accommodate a thinner form factor, some systems employ imaging system that may be folded optically in air space, allowing fairly thin form factors on order of 5″-6″ thick for a 37″ display, and even thinner, perhaps 2″ to 3″, for tiled folded imaging systems.
However, if thinness is desired, then wedge optics may sometimes be used to maintain thicknesses on order of, and possibly below, 1″ to 2″ for such similar sized displays. To achieve this, some systems employ a massively folded imaging system in a light guide form. However, such a design typically has at least one of the surfaces as a complex 2-dimensional curve profile, which has a thickness profile which starts moderate at the camera thick-end, and then grows smoothly toward first 3rd or so of length, then slopes with slight curvature toward a thin end.
In such systems, however, the imaging region is limited to the last one-half to two-thirds of the length or so towards the thin end. Such systems may thus use two wedges in a ‘head-to-toe’ configuration. In order to cover the full area of a display placed above the wedge imaging system, each wedge may cover about half the display region. Further, the surface curvature should be accurately fabricated, which may be difficult. In such system, all rays mapping from angle space near camera vision system to position space at the exit face of the wedge, tend to encounter the same number of bounces prior to exiting wedge.